On the original distribution of the asteriods. I.

The depletion of an initially uniform distribution of asteroids extending form Mars to Saturn, caused by the gravitational perturbations of Jupiter and Saturn, is calculated by numerical integration of the asteroid orbits. Almost all (about 85%) the asteroids between Jupiter and Saturn are ejected in the first 6000 years Most of the asteroids between the $\text{2}\text{3}$ Jupiter resonance (4.0 A.U.) and Jupiter are ejected in the first 2400 years with the exception of the stable librators (e.g., the Hilda group). Interior to the $\text{2}\text{3}$ resonance the depletion was small, and interior to the $\text{1}\text{2}$ resonance (3.3 A.U.) no asteroids were ejected in the first 2400 years.     

On the u.v. source of the night-time E region

The photo-ionization produced in the night-time E region by the total stellar u.v. continuum is considered. It is shown to be approximately equal to that produced by the scattered Lyman β above about 115 km.     

Conformal analogs of the Jordan-Brans-Dicke theory. I.

Recent cosmological observations of large-scale structures (red shift of type Ia supernovae) confirm that the universe is currently expanding at an accelerating rate and its dominant component is dark energy. This has stimulated the development of the theory of gravity and led to many alternative variants, including tensor-scalar ones. This paper deals with the role of conformal transformations in the Jordan-Brans-Dicke theory. Variants of intrinsic, conformally coupled, and Einstein representations are examined. In the Einstein representation an exact analytic solution for the standard cosmological model is obtained. It is expressed in terms of the relative energy contributions of ordinary matter Ω _m , the scalar field Ω _CK , and a term Ω_Λ related to the cosmological constant Λ . Information on the evolution of the universe for the case with a minimally coupled scalar field is given in the form of graphs.     

I.R. Radiation of the upper atmosphere

A theory of the i.r. radiation (2–20 μ) of the upper atmosphere (90–250 km height) has been developed. It includes the calculation of concentrations and temperatures as well as the analysis of atomic and molecular level population kinetics. Various excitation and quenching processes are analysed. Results are given for the following bands: NO (5.3μ), NO⁺(4.3μ.), CO (4.7 μ), N¹⁴N¹⁵ (4.4 μ), CO₂(4.3 and 15 μ), H₂O(2.7 and 6.3 μ), N₂O(4.5; 7.8 and 17μ), O₃(9.6 and 14.4 μ). The energy aspect of the problem is discussed. It is found that at a height of 120 km intensity in the region of 2 to 20 μ 3 to 10 is that of the 63 μ line of atomic oxygen. The comparison of theory with the experiment was carried out and satisfactory agreement obtained. The correlations of intensities in i.r. bands and emissions in visible and u.v. spectra were considered.     

Some results of investigations of aurorae and night airglow during the I.G.Y. and I.G.C.

A general review is given of the results of the airglow and auroral investigations during I.G.Y and I.G.C. in the Institute for Atmospheric Physics of the Academy of Sciences of the U.S.S.R. A strong helium emission at 10830 Å has been discovered in sunlit aurorae and in the ordinary twilight airglow. It is now observed regularly. A detailed theory of this fluorescent emission has been developed. Extensive observations on the hydroxyl bands between 5000 and 12,000 Å have been carried out at a number of stations. Marked seasonal and geographical variations have been found in them. During intense aurorae the line-width of the 6300 Å emission from great altitudes increases. The effect has been studied using Fabry-Perot interferometers. Contributions have been made to knowledge on auroral morphology. The interpretation of some of the results which are described in the review are discussed.     

Fine Structure of the Core of the Blazar OJ 287. III. Polarized Emission

This conclusive paper summarizes the results of our studies of the fine and superfine structure of the blazar OJ 287 at wavelengths of 7 mm and 2 cm in polarized emission with angular resolution is 20 μas. The orientation of the polarization of its fragments is almost orthogonal to the motion of the flows, suggesting that the magnetic field of the structures is oriented along the direction of the flow velocity. This is determined by the rotation of the flows—the excitation of ring currents and the generation of a solenoidal magnetic field, which applies both to the arms along which the surrounding matter is transferred to the center, the northern (m = 16%) and southern (m = 5%) ones, and to the ejected flows carrying away an excess angular momentum. The polarization level of the jet and counterjet flows reachesm = 15–20%and rises as one recedes fromthe nozzle due to a decrease in the optical depth of the fragments. The polarization level of the counterjet at the nozzle exit reaches 10%, while that of the jet is considerably lower. This is related to the location of the jet nozzle in the opposite direction relative to the observer, the influence of the screen. The special position refers to the nozzles. The polarization level is m - 2%. In the case of outbursts, the polarization increases with brightness, λ = 7 mm. At λ = 2 cm there is an inverse dependence. The spectral index of outbursts lies within the range α = 0–0.8.     

Interpretation of the Radiation of Coronal Suprathermal Streams. I.

This is the first part of a series of two articles aimed at revealing the role of the Compton effect in scattering of the solar photospheric radiation by coronal suprathermal streams. The simplest situation of a single beam of electrons gyrating around the strength lines of magnetic field is considered. Attention is focused on the height-independent problem, in which the role of the spatial angle of incident radiation is ignored. Analytical expressions for the frequency change of interacting photons and for the proper cross-section of the scattering process are derived. The results of numerical calculations show that the effect may by significant even for moderate energies of fast electrons and will be observable only if the fractional density of fast electrons is not too small.     

On the 100-th anniversary of the birth of Academician V. A. Ambartsumian

A brief review is given of the applications of some methods, mainly developed at the Byurakan Observatory, to the statistics of flare stars. These developments originate in papers by Ambartsumian which led to the fundamental conclusion that a stage of flare activity is a natural stage in the evolution of red dwarf stars. In terms of their scientific value and novelty, the mathematical methods developed by Ambartsumian for solving specific astrophysical problems in the statistics of flare stars are just as significant as the astrophysical results obtained using these methods.     

Variant of the bimetric theory of gravitation. II. Energy-momentum tensor of the gravitational field

Starting from the invariance of action relative to coordinate transformations, differential conservation laws are established in the bimetric theory of gravitation with a Lagrangian that is quadratic with respect to “intensities.” Explicit expressions are found for the canonical and metric energymomentum tensors of the gravitational field, as well as for the tensor analog of the Landau-Lifshitz pseudotensor. Translated from Astrofizika, Vol. 43, No. 3, pp. 493-499, July–September, 2000.     

S.E.M.A.Ph.Or.E COMETAIRE,a tool for the study of the photochemical decomposition of probable large organic molecules in comets. first application: Polyoxymethylene

This paper presents a current experimental program concerning the study of the photochemical evolution of the organic matter ejected from the cometary nucleus. The aim of the work is to better understand, using laboratory simulations, the mechanisms which are involved in the degradation of the high molecular weight organics in cometary ices and dust when they are submitted to the warming up and to the bombardment of photons in the surrounding area of the Sun. This experimental study will establish correlations between the nucleus and the molecular composition of the coma. Furthermore, experimental data will provide useful information to bring to a close the question of the origin of the extended sources of H₂CO and CO. Polyoxymethylene, suspected to be present in the cometary nucleus, is often mentioned as a possible parent molecule for the extended source of H₂CO. In order to test this hypothesis, irradiation of POM has been performed at 147 nm. The preliminary results show effectively H₂CO as one photodegradation product as well as CO. C0₂ and HCOOH. Tentative detections of CH₃0CH₃, CH₃OCH₂OCH₃, CH₃OCHO and C₃H₆O₃ are also presented.     

Variant of the Bimetric Theory of Gravitation. III. Gravitational Radiation

Gravitational radiation in a variant of the bimetric theory of gravitation is investigated in the case of slow motions and weak fields. Questions of the propagation velocity, polarization, and generation of a weak gravitational wave are considered. The Peters-Matthews coefficients and the dipole emission coefficient are determined.     

Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes

The Earth’s atmosphere is an integral part of the detector in ground-based imaging atmospheric Cherenkov telescope (IACT) experiments and has to be taken into account in the calibration. Atmospheric and hardware-related deviations from simulated conditions can result in the mis-reconstruction of primary particle energies and therefore of source spectra. During the eight years of observations with the High Energy Stereoscopic System (H.E.S.S.) in Namibia, the overall yield in Cherenkov photons has varied strongly with time due to gradual hardware aging, together with adjustments of the hardware components, and natural, as well as anthropogenic, variations of the atmospheric transparency. Here we present robust data selection criteria that minimize these effects over the full data set of the H.E.S.S. experiment and introduce the Cherenkov transparency coefficient as a new atmospheric monitoring quantity. The influence of atmospheric transparency, as quantified by this coefficient, on energy reconstruction and spectral parameters is examined and its correlation with the aerosol optical depth (AOD) of independent MISR satellite measurements and local measurements of atmospheric clarity is investigated.